The present invention relates to a non-flammable rigid foam including filler material on the basis of phenolic resins and furane resins having a bulk density of 50 kg/m.sup.3 to 450 kg/m.sup.3 and which complies with the requirements according to DIN 4102 and DIN 53436 so that it can be used as a non-flammable building material.
Phenolic resin foam materials are manufactured already in nominal densities of 40 to 100 kg/m.sup.3. Because of their comparatively high closed cell contents of about 75% they are used in buildings mainly as a thermal insulator. Such duroplastics foam materials, because of their 3-dimensional cross linkage are subjected in the event of fire primarily to carbonisation. The resulting carbon layer protects the underlying foam against further attack by flame and in addition this carbon layer in the event of pyrolysis gases catching fire, brings about an extinguishing of the flame.
The combustion performance is a process which takes place at the surface of the foam material, i.e. the extent of burning is determined by the surface area available, which in the case of foam materials having bulk densities as low as 40 kg/m.sup.3 may be very large. As a consequence thereof the combustible material anywhere within the range of flames and radiation is pyrolysed almost totally. This is further promoted by a certain degree of closed cell characteristics and the low thermal conductivity resulting therefrom which creates a heat build-up. This lends additional support to the pyrolysis and the combustion process.
In the case of phenolic resin foams the thermal stability may be up to about 130.degree. C. and for short durations up to 250.degree. C. The emission of volatile gases commences at 270.degree. C. and these may briefly burn when exposed to an open flame. As from 400.degree. C. only glimmering is to be observed which is caused by oxidation processes at the surface of the solid carbon resins. The addition of boric acid to phenolic resins acts as a flame protector. However, since boric acid is a slow acting curing agent, the shelf life of the phenolic resin is limited to 24 hours, wherefore the addition of boric acid as a flame protecting agent to phenolic resin mixtures results in processing difficulties, more particularly in that the addition is possible only immediately prior to processing.
J. Troitsch in Kunststoffe 69/9; page 558-561 (1979) points out that only few inorganic compounds exist which are suitable for use as a flame protecting agent in plastics. Aluminium hydroxide and boron-containing compounds are employed for this purpose since they can be incorporated in plastics.
J. Greber and D. J. Braun describe in Plastverarbeiter 33/1; page 43-46 (1982) that aluminium hydroxide can be used as flame retarding filler for unsaturated polyester resins. In order to produce building components which when subjected to fire testing according to DIN 4102 are classified in Class B1 (flame resistant), filler contents of more than 55 mass % are needed. However, the need for such high filler contents results in substantial processing problems which can be overcome only partly by the use of special aluminium hydroxides. Since the fire performance of materials depends not only on their contents of flame protecting agents in the mixture, but also on the design configuration of the testing bodies, the provision of unsaturated polyester resins with aluminium hydroxide as a flame protection agent creates more problems than the fire-proofing with conventional halogen-antimony systems.
A non-flammable material which does not evolve toxic fumes is known from DE-OS No. 28 25 295 on the basis of phenolic resins and furfuryl alcohol. The material comprises 62-66 mass % aluminium oxide or aluminium hydroxide as an inorganic filler and may in addition contain up to 3 mass % finely divided silicic acid and other components. A closed or rigid foam having a bulk density of 500 g/l can be produced by the addition of a bloating agent.
However, the material suffers from a number of disadvantages.
Because of the use of organic sulpho acids as a single component in the curing agent system, the cured finished product is hygroscopical and is moreover, as a result thereof subject to a prolonged final curing period.
It was found that due to the high density the final curing period for the attainment of the ultimate strength amounts to several weeks. Morever, this material is highly corrosive in respect of metallic surfaces.
Due to the high viscosity of the reaction mixture a substantial non-homogeneous foam mixture results from foaming.
Moreover, when exposed to fire, the content of sulphur dioxide in the smoke or pyrolysis gas is still very high.